The present invention relates to a horizontal hobbing machine for cutting a tooth form on a work piece supported around a central shaft provided substantially horizontal.
A hobbing machine for machining a gear by cutting is a typical machine tool for machining a gear. Hobbing machines are classified into a vertical hobbing machine for cutting a tooth form in a work piece supported around a central shaft provided substantially vertical, and a horizontal hobbing machine for cutting a tooth form in a work piece supported around a central shaft provided substantially horizontal.
An example of the conventional horizontal hobbing machine will now be described with reference to FIGS. 1 to 3. As is shown in FIGS. 1 to 3, a headstock 2 and a tailstock 3 are slidably supported on a bed 1. A work piece 4 is rotatably supported around a horizontally situated shaft between the headstock 2 and tailstock 3.
On the other hand, a saddle 5 is slidably supported on the bed 1. A head 6 is supported on the saddle 5. A hob 7 of a high speed tool steel is supported on the head 6. The hob 7 is rotated by a main shaft motor 8.
The head 6 is provided with a coolant nozzle 9. A coolant is supplied to a cutting section from the coolant nozzle 9. A chip exhaust groove 10 is provided on the bed 6. The groove 10 is provided with an exhaust port 11 inclined rearward of the present machine (horizontal hob machine: bed 1). Controls necessary for generating a tooth form, e.g. rotation of work 4, rotation and radial feed of hob 7, etc., are effected on the basis of commands from a control board 12.
In the above-described hobbing machine, while the work piece 4 is being rotated, the hob 7 is driven by the main shaft motor 8. The hob 7 and work piece 4 are thus engaged and a tooth form is generated on an outer periphery of the work piece 4. In this case, the rotating hob 7 is radially fed to the work piece 4 by sliding the saddle 5, thereby generating a predetermined tooth form on the work piece 4.
During the cutting process, a coolant is supplied to the cutting section from the coolant nozzle 9, thus lubricating and cooling the cutting section and washing away produced cut chips. The chips washed away with the coolant from the cutting section flow through the chip exhaust groove 10 on the bed 1 along with the coolant, and is drained out of the machine (horizontal hob machine: bed 1) from the exhaust port 11 to be recovered.
In the field of hobbing machines, too, various improvements have been made in order to enhance productivity and to reduce manpower. In addition, in these years, there is a demand for taking measures to protect the environment.
A measure for protecting the environment in the field of hobbing machines is a so-called "dry-cutting" process in which cutting is performed without using a coolant. The use of the coolant not only deteriorates the working environment due to malodor or dispersion, but also causes air pollution due to treatment of waste oil.
The main problems to be solved in adopting the dry-cutting process in the field of hobbing machines are wear of the hob and disposal of chips. The wear of the hob can be reduced, for example, by substituting a hob of cemented carbide for the hob 7 of high speed tool steel.
As regards the disposal of chips, however, there is no satisfactory measure, and this is the most serious problem in the dry-cutting process. If the coolant is used, the chips are washed away with the coolant and exhausted out of the machine (horizontal hobbing machine: bed 21). In the dry-cutting process using no coolant, however, chips will remain and accumulate in respective parts of the hobbing machine. Consequently, the chips will be caught among the sliding parts or operating parts of the hobbing machine, and normal operations will be hindered. Moreover, heat of chips is transmitted to the respective parts of the hobbing machine, resulting in thermal deformation and deterioration in machining precision.
The object of the present invention is to provide a horizontal hobbing machine capable of efficiently disposing of chips even in the dry-cutting process.